1. Field of the Invention
Embodiments of the present invention generally relate to a method of treating a tubular string using a pigtrain.
2. Description of the Related Art
Pipeline pigs are propelled by fluid pressure through the interior of pipelines to clean wax, sludge, scale, debris, and other materials from the inner surfaces of the pipeline. Pipeline pigs may also be used to fill a pipeline with water for hydrotesting and remove the water once testing is finished. Pipeline pigs may also be used to verify tolerances of the pipeline and inspect for corrosion. Pipeline pigs may also be used to remove accumulated liquids or solids in pipelines. Pipeline pigs may also be used to separate different types of fluids which may be traveling through the same pipeline.
For certain levels of pipeline cleanliness, it is necessary to employ detergent, such as a surfactant and/or an acidic solution. Such a method is discussed and illustrated in U.S. Pat. No. 5,230,842, which is herein incorporated by reference in its entirety. The '842 patent discloses launching a pigtrain having a lead pig 72, a trail pig 72, and an acidizing fluid 74 positioned between the pigs through a pipeline 10 back and forth until a determination is made that a inner surface of the pipeline is sufficiently clean. The trail pig 72 is propelled using pressurized air supplied via the launcher.